Livestock redistribute runoff and sediments in semi-arid rangeland areas

Abstract. Semi-arid areas where grazing is the main land use exhibit a "three-phase-mosaic" pattern of dominant surface patches: shrubs, trampling routes, and intershrub areas. This pattern differs from the "two-phase mosaic" seen in grazing-free semi-arid areas. The patches might create a positive feedback process in which enhanced infiltration beneath shrubs minimizes overland flow from under their canopies, thereby strengthening the sink–source mechanism by which overland flow generated between shrubs rapidly infiltrates into the soil beneath them, where it deposits soil particles, litter, nutrients and organic matter, thereby enhancing infiltration by changing the local microtopography, and improving soil properties. To analyze sink–source relationships among the patches in grazed areas in rangelands of the semi-arid northern Negev region of Israel, we constructed small runoff plots, 0.25–1.0 m2 in area, of five types: shrub (Sarcopoterium spinosum), intershrub, route, route–shrub combination, and intershrub–shrub combination. The shrubs always occupied the downslope part of the plot. Overland flow and sediment deposits were measured in all plots during 2007/8 and 2008/9. The combined plots yielded much less overland flow and sediments than intershrub, routes and shrub ones, indicating that the shrubs absorbed almost all the yields of the upper part of their plots. The shrubs generated less runoff and sediments than routes and intershrubs; runoff flows from the routes and intershrubs were similar; sediment yield was highest in the intershrubs. Thus, runoff yield exhibited a two-phase mosaic pattern, and sediment yield, i.e., soil erosion, a three-phase mosaic pattern.

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Livestock redistribute runoff and sediments in semi-arid rangeland areas

Solid Earth Discussions ◽

10.5194/sed-6-3197-2014 ◽

2014 ◽

Vol 6 (2) ◽

pp. 3197-3226

Author(s):

P. Sarah ◽

M. Zonana

Keyword(s):

Sediment Yield ◽

Overland Flow ◽

Arid Areas ◽

Mosaic Pattern ◽

Two Phase ◽

Surface Patches ◽

Sediment Deposits ◽

Three Phase ◽

Almost All ◽

Semi Arid

Abstract. Semi-arid areas where grazing is the main land use exhibit a "three-phase-mosaic" pattern of dominant surface patches: shrubs, trampling routes, and intershrub areas. This pattern differs from the "two-phase mosaic" seen in grazing-free semi-arid areas. The patches might create a positive feedback process in which enhanced infiltration beneath shrubs minimizes overland flow from under their canopies, thereby strengthening the sink/source mechanism by which overland flow generated between shrubs rapidly infiltrates into the soil beneath them, where it deposits soil particles, litter, nutrients and organic matter, thereby enhancing infiltration by changing the local microtopography, and improving soil properties. To analyze sink/source relationships among the patches in grazed areas in rangelands of the semi-arid northern Negev region of Israel we constructed small runoff plots, 0.25–1.0 m2 in area, of five types: shrub (Sarcopoterium spinosum) (SH); intershrub (IS); and route (RU); route/shrub combination (RS); and intershrub/shrub combination (SI). The shrubs always occupied the downslope part of the plot. Overland flow and sediment deposits were measured in all plots during 2007/2008 and 2008/2009. The combined plots – SI and SR – yielded much less overland flow and sediments than IS, RU and SH, indicating that the shrubs absorbed almost all the yields of the upper part of their plots. The shrubs generated less runoff and sediments than routes and intershrubs; runoff flows from the routes and intershrubs were similar; sediment yield was highest in the intershrubs. Thus, runoff yield exhibited a two-phase mosaic pattern, and sediment yield, i.e., soil erosion, a three-phase mosaic pattern.

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"Partial area contribution" and "Overland flow discontinuity": from humid to arid hillslopes

10.5194/egusphere-egu2020-3059 ◽

2020 ◽

Author(s):

Hanoch Lavee

Keyword(s):

Soil Moisture ◽

Overland Flow ◽

Infiltration Rate ◽

Dead Sea ◽

Livestock Grazing ◽

Rainfall Simulation ◽

Arid Areas ◽

Shallow Subsurface ◽

Partial Area ◽

Semi Arid

In humid temperate areas, where infiltration rate and soil moisture are high the hillslopes are draining mainly via shallow subsurface flow. Overland flow is seldom generated on the very low parts of hillslopes when the soil is saturated up to the surface. This spatial pattern is known as &#8220;partial area contribution&#8221;.In contrary, in arid areas, where the soil moisture is hygroscopic most of the time, overland flow is generated not because of soil saturation conditions but only when rainfall intensity is higher than the infiltration rate.&#160;&#160;Nevertheless, we found a &#8220;partial area contribution&#8221; pattern in several arid and semi-arid areas due other controlling factors:<ol><li>In eastern Sinai, under rainfall simulation experiments on scree slopes, due to high spatial differences in the soil texture, runoff coefficient in the gullies was almost 100% while in the very permeable interfluves runoff wasn&#8217;t generated at all. Overland flow was generated, therefore, only in the gullies (Lavee ,1973; Yair & Lavee ,1976).</li> <li>In an instrumented experimental watershed in the Northern Negev, the specific overland flow yield from long plots ,extending from the divide to the slope base (around 60m in length), was consistently lower than the combined specific overland flow yield from the adjacent two short plots (around 30m in length), draining the upper and the lower sections of the hillslope, respectively. This means that the overland flow is discontinuous and at least part of the overland flow that was generated at the upper part of the hillslope infiltrated, in most overland flow events, into the soil, before reaching the slope base. In other words, only the lower part of the hillslope contributes, in most cases, overland flow to the channel. Such overland flow discontinuity is controlled by: 1. The typical short duration of rain showers in arid areas. As more than 80% of the rain showers last for less than 15 minutes, the total flow duration is usually shorter than the concentration time. 2. The spatial distribution of infiltration rate. In this case it was mainly the relatively high infiltration rate in the colluvial cover at the lower part of the hillslopes in part of the study area that absorbed large amount of the water flowing from the upper part of the hillslopes (Lavee, 1982; Yair & Lavee, 1985; Lavee & Yair, 1990).</li> <li>In an experimental project along a climatological transect, running from the Mediterranean climate near Jerusalem to the extreme arid climate near the Dead Sea, the main reason for the overland flow discontinuity, especially in the semi-arid area, was the mosaic pattern of &#8220;source patches&#8221;, on which overland flow was generated, and &#8220;sink patches&#8221;, in which at least part of the direct rain and the incoming overland flow infiltrated. This pattern is produced by different processes, mainly via the effect of vegetation, but also due to the effects of micro-topography, big stones, especially if they are partly embedded in the soil, and livestock grazing (Lavee & Poesen, 1991; Lavee et al., 1998; Stavi et al., 2008).</li> </ol>

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Understanding runoff processes in a semi-arid environment through isotope and hydrochemical hydrograph separations

Hydrology and Earth System Sciences ◽

10.5194/hess-19-4183-2015 ◽

2015 ◽

Vol 19 (10) ◽

pp. 4183-4199 ◽

Cited By ~ 27

Author(s):

V. V. Camacho Suarez ◽

A. M. L. Saraiva Okello ◽

J. W. Wenninger ◽

S. Uhlenbrook

Keyword(s):

Surface Water ◽

Overland Flow ◽

Hydrological Process ◽

Arid Areas ◽

Runoff Generation ◽

Deep Groundwater ◽

Direct Runoff ◽

Total Runoff ◽

Semi Arid

Abstract. The understanding of runoff generation mechanisms is crucial for the sustainable management of river basins such as the allocation of water resources or the prediction of floods and droughts. However, identifying the mechanisms of runoff generation has been a challenging task, even more so in arid and semi-arid areas where high rainfall and streamflow variability, high evaporation rates, and deep groundwater reservoirs may increase the complexity of hydrological process dynamics. Isotope and hydrochemical tracers have proven to be useful in identifying runoff components and their characteristics. Moreover, although widely used in humid temperate regions, isotope hydrograph separations have not been studied in detail in arid and semi-arid areas. Thus the purpose of this study is to determine whether isotope hydrograph separations are suitable for the quantification and characterization of runoff components in a semi-arid catchment considering the hydrological complexities of these regions. Through a hydrochemical characterization of the surface water and groundwater sources of the catchment and two- and three-component hydrograph separations, runoff components of the Kaap catchment in South Africa were quantified using both isotope and hydrochemical tracers. No major disadvantages while using isotope tracers over hydrochemical tracers were found. Hydrograph separation results showed that runoff in the Kaap catchment is mainly generated by groundwater sources. Two-component hydrograph separations revealed groundwater contributions of between 64 and 98 % of total runoff. By means of three-component hydrograph separations, runoff components were further separated into direct runoff, shallow and deep groundwater components. Direct runoff, defined as the direct precipitation on the stream channel and overland flow, contributed up to 41 % of total runoff during wet catchment conditions. Shallow groundwater defined as the soil water and near-surface water component (and potentially surface runoff) contributed up to 45 % of total runoff, and deep groundwater contributed up to 84 % of total runoff. A strong correlation for the four studied events was found between the antecedent precipitation conditions and direct runoff. These findings suggest that direct runoff is enhanced by wetter conditions in the catchment that trigger saturation excess overland flow as observed in the hydrograph separations.

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Understanding runoff processes in a semi-arid environment through isotope and hydrochemical hydrograph separations

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-975-2015 ◽

2015 ◽

Vol 12 (1) ◽

pp. 975-1015 ◽

Cited By ~ 1

Author(s):

V. V. Camacho ◽

A. M. L Saraiva Okello ◽

J. W. Wenninger ◽

S. Uhlenbrook

Keyword(s):

Surface Water ◽

Overland Flow ◽

Hydrological Process ◽

Arid Areas ◽

Runoff Generation ◽

Deep Groundwater ◽

Direct Runoff ◽

Total Runoff ◽

Semi Arid

Abstract. The understanding of runoff generation mechanisms is crucial for the sustainable management of river basins such as the allocation of water resources or the prediction of floods and droughts. However, identifying the mechanisms of runoff generation has been a challenging task, even more so in arid and semi-arid areas where high rainfall and streamflow variability, high evaporation rates, and deep groundwater reservoirs increase the complexity of hydrological process dynamics. Isotope and hydrochemical tracers have proven to be useful in identifying runoff components and their characteristics. Moreover, although widely used in humid-temperate regions, isotope hydrograph separations have not been studied in detail in arid and semi-arid areas. Thus the purpose of this study is to determine if isotope hydrograph separations are suitable for the quantification and characterization of runoff components in a semi-arid catchment considering the hydrological complexities of these regions. Through a hydrochemical characterization of the surface water and groundwater sources of the catchment and two and three component hydrograph separations, runoff components of the Kaap Catchment in South Africa were quantified using both, isotope and hydrochemical tracers. No major disadvantages while using isotope tracers over hydrochemical tracers were found. Hydrograph separation results showed that runoff in the Kaap catchment is mainly generated by groundwater sources. Two-component hydrograph separations revealed groundwater contributions between 64 and 98% of total runoff. By means of three-component hydrograph separations, runoff components were further separated into direct runoff, shallow and deep groundwater components. Direct runoff, defined as the direct precipitation on the stream channel and overland flow, contributed up to 41% of total runoff during wet catchment conditions. Shallow groundwater defined as the soil water and near-surface water component, contributed up to 45% of total runoff, and deep groundwater contributed up to 84% of total runoff. A strong correlation for the four studied events was found between the antecedent precipitation conditions and direct runoff. These findings suggest that direct runoff is enhanced by wetter conditions in the catchment which trigger saturation excess overland flow as observed in the hydrograph separations.

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Grazing-Induced Modification of a Semi-Arid Rangeland from a Two-Phase to a Three-Phase Mosaic Geo-Ecosystem

Arid Land Research and Management ◽

10.1080/15324982.2011.631691 ◽

2012 ◽

Vol 26 (1) ◽

pp. 79-83 ◽

Cited By ~ 7

Author(s):

Ilan Stavi ◽

Hanoch Lavee ◽

Eugene Ungar ◽

Pariente Sarah

Keyword(s):

Two Phase ◽

Three Phase ◽

Semi Arid ◽

Arid Rangeland

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Understanding rice innovation needed for smallholder farmers in semi-arid area of East Nusa Tenggara, Indonesia

E3S Web of Conferences ◽

10.1051/e3sconf/202130603009 ◽

2021 ◽

Vol 306 ◽

pp. 03009

Author(s):

Yohanis Ngongo ◽

Alfonso Sitorus ◽

Cristine W. Huwae ◽

Rizky Prayogo Ramadhan ◽

Nuning Argo Subekti

Keyword(s):

Smallholder Farmers ◽

Arid Areas ◽

Target Groups ◽

Rice Productivity ◽

Rice Farmers ◽

Timor Leste ◽

State Boundary ◽

Agricultural Innovations ◽

Almost All ◽

Semi Arid

Rice is grown in various environments across semi-arid areas of ENT province. This paper elaborates agricultural innovations delivered to the smallholder rice farmers and highlights their responses/adaptability. The research conducted in the state boundary of Indonesia-Timor Leste as part of AIAT-ENT program. The study showed that farmers having more access to rice innovation sources tend to adopt better and willing to purchase for external inputs. By adopting introduced rice innovations, co-operatives farmers in state boundaries were able to improve rice productivity from 1 – 2 ton/ha to 5 – 7.2 ton/ha. After 3 years of AIS implementation, almost all farmers have been continuously HYVs of rice. However, the sustainability of the innovation’s adoption has commonly disrupted by the availability of external inputs. Numerous rice-related innovations have been introduced; however, smallholder farmers were keen to adopt only limited ones that suitable with their specific environment and household circumstances. The study concluded that rice innovations delivered to improve rice productivity in semi-arid areas should be focus on specific target groups that suitable their environments and household’ circumstances. Rice-related innovations should be delivered in the broader context not merely to increase rice productivity, rather to improve smallholder semi-arid farmers’ resilience for food security.

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Overland runoff erosion dynamics on steep slopes with forages under field simulated rainfall and inflow

10.5194/egusphere-egu2020-1694 ◽

2020 ◽

Author(s):

Changjia Li ◽

Chengzhong Pan

Keyword(s):

Flow Velocity ◽

Friction Factor ◽

Sediment Yield ◽

Soil Loss ◽

Overland Flow ◽

Arid Environments ◽

Simulated Rainfall ◽

Stream Power ◽

Erosion Processes ◽

Semi Arid

Although numerous studies have acknowledged that vegetation can reduce erosion, few process-based studies have examined how vegetation cover affect runoff hydraulics and erosion processes. We present field observations of overland flow hydraulics using rainfall simulations in a typical semi-arid area in China. Field plots (5 m &#215; 2 m) were constructed on a loess hillslope (25&#176;), including bare soil plot as control and three plots with planted forage species as treatments&#8212;Astragalus adsurgens (A. adsurgens), Medicago sativa (M. sativa) and Cosmos bipinnatus (C. bipinnatus). Both simulated rainfall and simulated rainfall + inflow were applied. Forages reduced soil loss by 55&#8211;85% and decreased overland flow rate by 12&#8211;37%. Forages significantly increased flow hydraulic resistance expressed by Darcy-Weisbach friction factor by 188&#8211;202% and expressed by Manning&#8217;s friction factor by 66&#8211;75%; and decreased overland flow velocity by 28&#8211;30%. The upslope inflow significantly increased overland flow velocity by 67% and stream power by 449%, resulting in increased sediment yield rate by 108%. Erosion rate exhibited a significant linear relationship with stream power. M. sativa exhibited the best in reducing soil loss which probably resulted from its role in reducing stream power. Forages on the downslope performed better at reducing sediment yield than upslope due to decreased rill formation and stream power. The findings contribute to an improved understanding of using vegetation to control water and soil loss and land degradation in semi-arid environments.

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The generated power of multipole induction generator with secondary winding on the stator

Scientific Journal of Riga Technical University Power and Electrical Engineering ◽

10.2478/v10144-009-0006-2 ◽

2009 ◽

Vol 25 (25) ◽

pp. 31-34

Author(s):

Guntis Diļevs ◽

Edgars Jakobsons

Keyword(s):

Rotation Speed ◽

Induction Generator ◽

Two Phase ◽

Three Phase ◽

Secondary Winding

The generated power of multipole induction generator with secondary winding on the statorThis paper posses the construction of induction generator, which has the ability to operate at a low rotation speed. This generator can be applied for directly driven turbine without using the gearbox. The generator is multi pole with all of the windings placed on the stator. Rotor is tooth-like and has no windings on it. Primary winding is three phase, secondary winding is two phase.

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